1. Field of the Invention
This invention relates to product application control systems. More particularly, this invention relates to a product application control system for use with a distributed network.
2. Description of the Prior Art
Present agricultural product applicator control systems are designed for simple closed looped control of a multiple loop system. At present, the maximum amount of loops that can be added to a network typically would approach 10. Beyond this value, the overall packet structure and network control would become cumbersome, requiring significant redesign of the overall system.
A typical modern system is laid out with a host controller located within the cab of a vehicle, made up of a processor with associated input and output devices. This host is typically directly linked to a controller located within the cab, which is responsible for all communication to devices on the chassis of the vehicle. Such a system is shown in Ortlip U.S. Pat. No. 4,630,773 issued Dec. 23, 1986 entitled "Method and Apparatus for Spreading Fertilizer". Another system is shown in Monson et al., U.S. Pat. No. 5,220,876 issued Jun. 23, 1993 entitled "Variable Rate Application System" and assigned to the Assignee of the present invention.
In known systems such as those stated above, the addition of loops to the control requirements adds great complexity to the system wiring. This results in a realistic limit to the amount of loops that can be added to a single system. Beyond this limit, the amount of wiring and routing for the wiring becomes a matter of greater importance. At present, it is felt that a value of 10 loops is the approximate limit for a single host system as stated hereinbefore.
Software construction also places many constraints on the design and application of a control system, as the common top down design has certain flow characteristics that define a specific flow path within the operating system. This also limits the effective amount of devices that can be controlled with a single system, as eventually the communication link to the devices becomes the limiting factor.
The aforementioned software construction implies that any changes in requirements, such as the inclusion of an additional loop on the vehicle, often causes sweeping changes within the code. This also has obvious trickle-down effects that are not desired within the flow structure of the program.
Thus, debugging and testing become required parts of the system maintenance, requiring large amounts of capital and time to assure a simple change has not caused greater errors elsewhere in the system (often occurring in totally unrelated places).
For the aforementioned reasons, it becomes apparent that existing product application control system designs are by no means desirable, and an entirely new approach is required. As will be demonstrated below, the present invention provides a solution to this dilemma.